Optical networks generally comprise transmission components that are designed to transmit bands of wavelengths over reasonable distances. The bands of wavelengths generally comprise signals intended for a plurality of customers/users. Thus, a single optical fiber can be used to simultaneously transmit a plurality of signals that are subsequently divided for delivery. Similarly, individual signals are combined for transmission over common lines prior to eventual division for routing and/or delivery. Individual bands thus are divided into smaller wavelength ranges corresponding to signals relating to individual users, including aggregations of a few users, and multiplexing and de-multiplexing functions can be used to convert between combined signals for common lines and individual signals for routing and/or interfacing with individual users.
Arrayed waveguide gratings (AWG) are optical circuit components that are designed to perform multiplexing and de-multiplexing functions for optical signals. Planar optical circuits provide a convenient format for AWGs that can be placed at desired locations within an optical network. An AWG generally comprises two broadly transmitting optical elements, such as slab waveguides, that are connected by an array of waveguides with a range of lengths. The length differences of the dispersive waveguide array are selected to result in appropriate constructive and destructive interference within a slab waveguide between light transmitted by the array of waveguides such that a multi-chromatic signal is spatially spread out by the interference pattern such that smaller wavelength ranges can be separately transmitted following de-multiplexing. Similarly, transmission of light in the opposite direction results in the transmission of a combined multi-chromatic signal relative to a group of input signals with different wavelengths within a range of wavelengths. The arrayed waveguide may thus be configured with an integrative side and a dispersive side, with light passage from the integrative side to the dispersive side providing decomplexation of a signal into a multi-chromatic signal, and vice versa, with passage of light from the dispersive side to the integrative side providing integration of a multi-chromatic signal. Basic principles of an AWG are well known in the art and are described for instance in U.S. Pat. No. 5,002,350.